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for in loop

A "for in" loop is a construct that allows you to iterate over elements in a table or array without specifying the loop control variables or indices. In Lua, the "for each" loop is achieved using the for keyword in combination with an iterator function ( pairs(), ipairs(), os.fs.glob()).

The specific form of a "for each" loop in Lua uses the for k, v in pairs(table) do syntax, where:

  • k is a variable that represents the key of the current element.

  • v is a variable that represents the value associated with the key.

Here's a simple example using a Lua table:

-- Example table   
local myTable = {key1 = "value1", key2 = "value2", key3 = "value3"}   
   
-- Iterate over key-value pairs using pairs()   
for k, v in pairs(myTable) do   
  trace(k, v)   
end

In this example, for each iteration the pairs function returns an iterator function that produces key-value pairs from myTable.

k takes on the key, and v takes on the corresponding value. The loop body (the print(k, v) statement in this case) is executed for each pair.

The output of this example would be:

key1 value1   
key2 value2   
key3 value3

This type of loop is convenient when you want to iterate over the elements of a collection without explicitly dealing with indices. It's often used with tables in Lua, but it can be applied to other iterable data structures as well.